This invention relates generally to pipeline corrosion detecting apparatuses. More particularly, the invention relates to an apparatus for inserting and retrieving coupons from large diameter pipelines to periodically check for corrosion and wear of the pipeline due to flow of medium such as corrosive fluids or suspensions through the pipeline.
It is known in the prior art that the flow of fluids or suspensions through pipelines can result in corrosion and deterioration of the pipeline at its inner wall. Such pipelines may often be inaccesible due to being buried underground or otherwise concealed. It has been the practice to insert test coupons into the pipeline. The test coupons are constructed of a suitable material such as the pipeline itself, so that the corrosive effects on the coupon are indicative of the corrosive effects on the pipeline. In large diameter pipeline, such as 24-inch and 36-inch pipelines, the apparatus for inserting the coupon generally includes an elongated shaft housing assembly extending from the pipeline. So far as known, it has been a practice in the past to retrieve the coupon through the elongated shaft housing assembly. In the case of large diameter pipelines, this would require extended heights for removal of a shaft, which mounts coupons on one end thereof, through the shaft housing assembly. The extended height may make it difficult for a single operator to retrieve the coupons.